1. Field of the Invention
The present invention relates to an apparatus and a method of forming an image, and more particularly, to an apparatus and a method of forming an image, by which less time is taken from picking a document to discharging the document in a high resolution scanning operation.
2. Description of the Related Art
In general, an image forming apparatus is an apparatus that receives an image signal and transfers the image signal onto a document as a visual image. On the other hand, an image forming apparatus having an image scanning function is an image forming apparatus having a function of reading an image recorded on a document and converting the image into digital image information so as to be displayed on another document or a display device, for example, a facsimile or a scanner. The image forming apparatus having the scanning function includes a conveying unit that transports a document, on which an image is recorded, into the image forming apparatus along a predetermined document conveying path and discharges the document out of the image forming apparatus, and a scanning unit disposed on the document conveying path. The conveying unit generally includes various kinds of rollers, and a driving unit such as a motor or a clutch for driving the rollers. The scanning unit includes a charge coupled device (CCD) module. When the document passes the CCD module, the image recorded on the document is read out.
However, in order to obtain high resolution digital image information of high resolution from the image scanning operation, the conveying speed of a document passing the CCD module should be slower than that for a document having relatively lower resolution. Therefore, in the conventional image forming apparatus, in a case where the resolution of the scanning document is high, the speed of conveying the document is lowered throughout the entire conveying path, that is, from picking the document to discharging the document. Accordingly, it takes a lot of time from the picking operation to the discharging operation in the high resolution scanning operation, and consequently, scanning efficiency of the image forming apparatus is degraded. Also, a rotating speed of a pickup roller that picks up the document is too slow to perform the pickup operation well.